i dont know why this doesnt work? im picking a pair then picking each other shoe such that i dont pick its pair...?

Shouldn't it be 10C1 * 9C6 * 2^6 / 20C8 ?

We pick the complete pair (ten choices), then from the remaining nine pairs we must select six shoes, and no two shoes can be from the same pair, thus we are selecting six pairs (9C6) and beyond that we have two choices per pair, giving the 2^6 factor.

Originally Posted by stumped765

P(no complete pair)= 1-P(at least 1 complete pair)

which i would do in the same fashion as above but its not working so im missing something.

I would think P(no complete pair) would be simpler to compute directly than P(at least 1 complete pair), and the computation would proceed similarly to how I described above.